The present disclosure relates to a document reading apparatus that reads documents that are placed on a contact glass, and particularly relates to a document reading apparatus having a document size determining function.
Conventionally, an electronic copying machine, facsimile and the like are known as image forming apparatuses that are provided with a document reading apparatus that reads a document such as a photograph, text and the like on a contact glass. Of this kind of image forming apparatus, an image forming apparatus is know that first determines the document size of a document that is placed on the contact glass, then based on the determined document size, performs control of reading, selection of paper to be printed on and the like.
Typical technology of a method for determining document size will be explained. Only a specified position where the document is placed on the contact glass is read, and then using the image data of the read document, a black-and-white determining process is performed for a plurality of patches that correspond to the specified position of the document, and the document size is determined based on the results of the black-and-white determining process for each patch.